EP0214981A1

EP0214981A1 - Sealed electric accumulator and a method for manufacturing parts to the same

Info

Publication number: EP0214981A1
Application number: EP85902700A
Authority: EP
Inventors: Erik Sundberg
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-05-07
Filing date: 1985-05-07
Publication date: 1987-03-25
Also published as: FI864511A0; FI864511A; WO1985005227A1

Abstract

Accumulateur électrique, notamment accumulateur au plomb, comprenant un élément pourvu d'un récipient (2) étanche à l'électrolyte et au gaz, au moins une électrode poreuse positive (16), au moins deux électrodes poreuses négatives (12, 22) et un électrolyte en quantité suffisante pour obtenir le degré de décharge désiré. L'électrode positive (16) comprend au moins deux parties (25, 26) ayant chacune la forme de tubes triangulaires avec un côté plat tous les deux tubes à proximité de l'électrode négative et un côté plat tous les deux tubes à proximité de l'autre électrode négative. Dans les zones où les autres parties des côtés des triangles se rencontrent avec les parties des électrodes positives est placé un matéiau microporeux (38) consistant en un réservoir d'acide (18) pouvant recevoir une quantité prédéterminée d'électrolyte, constituant avec l'électrolyte dans les électrodes positives et dans les zones restantes (14, 24) recevant l'électrolyte, une quantité suffisante du degré de décharge recherché.Electric accumulator, in particular lead-acid accumulator, comprising an element provided with a container (2) impermeable to electrolyte and gas, at least one positive porous electrode (16), at least two negative porous electrodes (12, 22) and an electrolyte in sufficient quantity to obtain the desired degree of discharge. The positive electrode (16) comprises at least two parts (25, 26) each having the shape of triangular tubes with a flat side every two tubes near the negative electrode and a flat side every two tubes near the negative electrode. the other negative electrode. In the areas where the other parts of the sides of the triangles meet with the parts of the positive electrodes is placed a microporous material (38) consisting of an acid reservoir (18) capable of receiving a predetermined amount of electrolyte, constituting with the electrolyte in the positive electrodes and in the remaining areas (14, 24) receiving the electrolyte, a sufficient quantity of the desired degree of discharge.

Description

Sealed electric accumulator and a method for manufacturing¹ parts to the same

Technical field:

The present invention relates to an electric accumulator, par¬ ticularly lead accumulator, with an electrolyte and gas tight contai¬ ner and a positive porous electrode, at least two porous negative electrodes and electrolyte to an amount enough for the discharge degree which is desired . The positive electrode consists of at least two parts, each shaped as tube plates with a common upper frame. Furthermore, it relates to a method for the manufacturing of parts to the same, more exactly such parts manufactured from a porous material.

Background:

It is known there are lead accumulators , in which the electro¬ lyte is completely absorbed within the pores of the electrodes and separators . Furthermore the pores are not completely saturated with electrolyte which gives the generated gas, while being charged an opportunity to pass between the positive and the negative plates . Such arrangements are described in U .S . Patent No . 3,862,861 McClel¬ land et al and in U . S . Patent No. 4,421 ,832 Uba. These accumulators do not contain a sufficient amount of electrolyte to fully utilize the active material of the positive and negative electrodes . For this reason such cells are termed "unsaturated" (starved) electrolyte cells . It has been found that such cells may be operated over long periods of time completely closed without loss of water. They are also charac¬ terized as "oxygen recombining cells" .

It is well known that a lead accumulator needs specific quantities of each of three types of materials: Positive active material (PbOo) , Negative active material (Pb) and Electrolyte (H₂SO₄) . The amount of these materials have been known and fully discussed in standard texts (for example "Storage Batteries" by George Vinal) . In practice it is not possible to fully utilize all the active mate¬ rials in a cell. Active material utilization is dependent upon the cur¬ rent intensity . At low current intensities during ten hours or more , active material utilization may be several times as great than by short discharge periods during five to ten seconds , such as by starting a car engine . Thus accumulators designed for low discharge rates require substantially more electrolyte than cells designed for high discharge rates, but they are due to lack of electrolyte not very suitable for longer discharge periods . More commonly it can be said that in or¬ der to receive a good capacity at low discharge current intensity the volume of electrolyte required to get a good utilization of the positive and negative plates is about three times as great as the vo¬ lume of the positive plate (grid plus active material) . The volume of electrolyte outside of the electrodes varies depending on porosity of the active paste as the electrodes also containe considerable amounts of electrolyte.

The life of a lead accumulator depends on several factors . One of them is the thickness of the grid of the positive electrode. The thicker each lead string and the thicker the positive plate is , the longer is the life of the plate generally. Thus cells designed for low current intensities commonly include positive plates ranging from appro¬ ximately 4 mm to approximately 10 mm in thickness . If cells designed according to the teachings of U . S . patent No . 3 ,862,861 were designed for low current intensities an acid layer of 12-30 mm would be needed, i.e. 6-15 mm on each side of the positive electrode.

In open cells where the electrolyte is not intended to be com¬ pletely absorbed in the separators it is usual to have a considerable amount of acid over the plate set. There are two reasons to keep the electrolyte layers thin, i.e. the distance between the electrodes shall be small. First, the electrical resistance of the electrolyte layers will be relatively high in comparison to other parts of the electrode package. A cell with an electrode distance of for instance 6 mm will have a lower discharge than a cell with for instance 1 mm distance. This decreased voltage or waste capacity is particularly noticable at high discharges . The second reason to keep a small electrode distance in a cell with oxygen recombination is that the rate of recombination is inversely related to the distance between the positive and negative electrodes . In cells of this type oxygen gas will be produced at the positive plate before it is full charged and is transported via the separator to the negative plate which is oxidized . Oxygen will con¬ tinue to be produced at the positive plate as long as the cell is being charged and continues to oxidize the negative plate at the same rate as it is being charged . It is this feature that enables an oxygen recombination cell to operate over its lifetime without any loss of water. The degree of recombination determines the current intensity by charging during full-charging and for several reasons it should be as high as possible. Therefore the electrodes should be as close together as possible in order to provide a very thin electrolyte layer. The distance can vary from 0 , 1 mm to 3 mm . Above 3 mm the recom¬ bination is prohibitively low.

Two ways how the oxygen can be transported from the positive electrodes to the negative electrodes have been observed . According to the first way oxygen is soluted in the electrolyte and is carried to the negative plate by means of ordinary acid diffusion, which oc¬ curs within the cell. Another way is that gaseous oxygen passes from the positive plate to the negative plate where it reacts and oxi¬ dizes the same . In this case it is necessary to provide openings in the separator without electrolyte to permit the gas to flow.

This may be done by only partially filling the cell with electro¬ lyte whereby the separator will not be completely saturated with liquid. Also in the last mentioned mechanism it will be necessary to have an electrolyte between the plates in order to achieve a way for a ion transport. Therefore the separator must be very absorbant and act as a wick and not completely saturated with liquid for ion transport and at the same time have a pore structure with openings for gas transport between the electrodes . At normal pressures when the solu¬ tion of oxygen in acid is small, the latter form of oxygen transport is dominated, but the two ways are dependent on the distance between the electrodes . It is , however, possible to get a gas recombination with a short distance and a very controlled charge, *but the com¬ bination degree is less and the time of charging is longer.

Open lead accumulators are known having two relatively thin positive electrodes placed opposite each other in order to act to- gether as a single thick electrode. But these constructions have had an abundance of acid relative to the electrodes and full saturation of acid in all the cell.

Technical problem :

There are according to what is evident from the above many problems associated with the design of a closed battery for good per¬ formance at different operations . Thus no construction is known which gives a good utilization of the active lead material at low discharges and at the same time oxygen recombination at full charge . Certain problems are associated with bringing about a suitable porous material for this purpose.

The solution:

At the electric accumulator according to the present invention the positive electrode consists of triangle shaped tubes with a flat side of every two tubes close to the negative electrode and a flat side of every two tubes close to the other negative electrode. In those areas where the remaining triangel sides of the positive elec¬ trodes are meeting there is a micro porous material consisting of an acid reservoir.

The method according to the invention implies that those glass fibres forming the micro porous material, before forming takes place, are supplied with a substance such as a metal salt, which gives a stabilizing effect of the glass fibre bodj-' . The substance should be such that it will be saturated from the glass fibre body by the elec¬ trolyte so that the requisite pores are formed. The requirement is that the saturated substance can be received in the electrolyte with¬ out a damaging effect.

Advantages :

By means of the present invention an electric accumulator with a cell structure is provided, having ample electrolyte quantity even at a discharge with a low current strength for high capacity and excellent capacity at high discharge rate performance, due to the low internal resistance, long life and complete recombination of gas and furthermore a porous material is produced, suitable to be used in the accumulator. Brief description of the drawings :

Three embodiments of the battery according to the invention are illustrated on the accompanying drawings and are described be¬ low together with the method. In the drawings Fig. 1 is a view of a typical cell according to the invention ; Fig. 2 is a section on the line II-II of Fig. 1 where two parts of the positive plate have a com¬ mon upper frame and manufactured by triangle shaped tubes ; Fig. 3 shows likewise as in Fig. 2 a similar embodiment according to examp¬ le two with the difference that the cell also has separators ; Fig . 4 shows in a corresponding section as in Figs . 2 and 3 a further examp¬ le with separators , and Fig. 5 shows a section along the line V-V in Fig. 2 at the type of cell according to Fig. 2 with positive tube plates .

Preferred embodiments :

According to the preferred embodiements of the accumulator according to the invention the two parts of the positive plate are connected to a common upper frame by using a so called tube plate with every two tubes placed close to the negative electrode and every two tubes close to the other negative electrode. In order to have as large area as possible of the positive electrode to lie close to the negative electrode, whereby a thin electrolyte layer can be established, the tubes are triangle shaped, where every two tubes have one side of the triangle close to the negative electrode and eve¬ ry two tubes close to the other negative electrode. Totally for instan¬ ce eight tubes can be close to the one negative electrode and eight tubes close to the other negative electrode . The tube plate has like many other tube plates separate outer plates which are approximately half as large as the remaining tubes .

Fig. 1 shows a prismatic lead ^"cell with a jar body 2 and a lid 4 hermetically connected to the jar body . These two parts form a vessel, non-permeable for acid and gas . A positive pole 6 and a nega¬ tive pole 8 and a safety valve 10 are placed on the "upper side" of the vessel. (As the cell can work in all positions there is only one upper side during assembling . ) The reason for having a safety valve is that if the cell should be over charged with too high current strength or that the recombination of any other reason should not function , the safety valve must open in order to prevent the vessel from exp¬ losion .

In Figs . 2-5 a section of the wall of the vessel 2 is shown . A first negative plate is designated 12. This is a normal greased plate with a metallic lead bar carrying the active lead quantity . A separa¬ tor 14 (see Fig. 3) respectively 38 (se Fig. 4) is made from absor¬ bing material, which will be described in the following. A first part of the positive electrode is designated 16. Also this one is partly of conventional kind with a grid and positive material (PbO₂) . The side wall of the tube of the positive plate which is not facing the negative electrode is part of a side of an electrolyte reservoir 18. The inner wall of the next part 26 of the positive electrode forms the next wall in the acid reservoir together with vessels and lid walls . The reservoir 18 with the positive plates on each side forms the total positive electro¬ de. Outside this one is the next separator 24 (Fig. 3) and the other negative - electrode 22, which are identical to 14 and 12 respectively. The reservoir 18 is suitably filled with an absorbing material which can also be present above and under the electrodes . The absorbing material can be of the same kind as the separators 14, 24 consists of or even identical. The oxidation potential is highest at the separa¬ tors and less in the reservoir and the demand on oxidation permanen¬ ce is therefore highest for the separators .

The tubes have an acid reserve in the thick felted tube walls which are situated on the one hand between the tubes and on the other hand between the positive and the negative electrode. The thickness of the tube walls is suited for the amount of acid that is desired with consideration taken that the absorbing tube walls due to the oxygen transport should not be entirely saturated with elec¬ trolyte .

The absorbing material between the two positive single plates serves to keep the electrolyte in the reservoir 18 in place at diffe¬ rent positions of the cell, even when it is in an upside-down position. But the capillary forces in the separators 14 and 24 which are bal¬ anced with the corresponding capillary forces in the absorbing material in the reservoir makes it possible to have these separators non-satura- ' ted with electrolyte in order to give the gas from the positive electrode possibility to reach the negative electrode in gaseous form , at the same time as there is enough electrolyte for ion transport . In order that electrolyte from the reservoir shall not move to the separators and saturate these with electrolyte, the absorbing material in the reservoir must have approximately the same degree of non- saturation . On the other hand the thickness of the reservoir can be made sufficent in order to provide the cell with all the acid that is necessary for very long discharges . The most suitable way to establish separators of absorbing material with a degree of saturation which gives openings for the gas can be not to fill the cell with electrolyte to the brim of the plates . Another way is to charge the cells in upside-down position with a high current strength . The hydrogen and acid gases formed will drive away the electrolyte which leaks out.

The degree of saturation desired can depend on the working manner of the cell and the separators and the porosity of the absorbing material. It can vary from 98% to 80% with 90% till 95% as the best values of the full amount at saturated material.

In Fig. 2 numeral 2 is as stated earlier the vessel; 12 and 22 are the negative electrodes ; 16 the positive electrodes and their parts

25 and 26; 28 and 29 the positive substance in the tubes ; 32 and 34 electric conductive lead cross bars and 36 is an isolated plastic foil on the rear side of the conductor to let the current pass through the positive substance and not directly through the tube walls to the negative electrode.

Fig. 3 shows a similar embodiment with a somewhat thinner tube walls and where said micro porous separator 14 and 24 has been pla¬ ced between the positive and the negative electrode. Nor this one is completely saturated with elecgrolyte, 90-95% saturation is usually suitable .

Fig. 4 shows the third embodiment. Here the tube walls in the positive electrodes 16 (same numerals as previously) are still thinner. As a reservoir for the electrolyte not only the separators 14, 24 will be used but also an additional separator 38 between the parts 25,

26 of the positive electrodes . By the triangle shape of the electrodes this separator is pleated, see Fig. 4.

Fig. 5 shows a section along the line IV-IV in Fig. 2 of a cell with triangle shaped tubes and a common upper frame designated 19 in Fig. 5 for the negative electrodes 14, 24 and 20 for the parts 25, 26 for the positive electrodes 16. The upper frames are connec¬ ted with the poles 6, 8 and can alternatively be placed outside the lid 4. The tube plate, well known in the accumulator industry, con¬ sists of a number of vertical lead cross bars , where every cross bar is surrounded by a cylinder of lead dioxide. This one in turn is kept in place of a chemically resistant porous tube. Excellent tu¬ bes are made from braided glass fibre. At compressed micro glass separators macro spaces are avoided in which gas bubbles can be collected. The absorbing material in the reservoir 18 between the positive half plates can be of similar fiber material.

As it is important from the point of view of life that the posi¬ tive substance is supported from all direction in order not to increase the volume, the tubes are suitably manufactured from filted micro fibres of glass , and aforementioned, with a wall thickness so that the tubes can support each other and so that the total demand of acid in addition to what is inside the porous electrodes is stored in the tube walls , which naturally in spite of this should not be satura¬ ted with liquid in order to make oxygen transport possible.

Instead of uniform thick tube walls it is possible to have thin woven or braided tubes with reinforcements between the tubes . These reinforcements and reinforcements between the tubes and the negative electrode are made from felted fibre material, suitably glass with micro fibres , in order to increase the wall thickness and support the tubes . Tube shaped electrodes can also be raised of pleated pla¬ tes of felted micro fibres combinated with separators of the same material.

At closed cells which often shall be used in different positions the electrolyte shall be absorbed in a porous material as aforemen¬ tioned. At the three embodiments three different embodiments of the positive electrode have been mentioned in such a way that it will contain an electrolyte reservoir. At the first embodiment according to Fig. 2 the triangle shaped tubes, which form the parts of the positive electrode, are made with so large wall thickness that they form the pore volume which constitutes the reservoir. Where the tu¬ bes meet each other a double wall thickness is established relative to the sides opposite to the negative electrodes , if the tubes have unchanged wall thickness . In this case the demand on requisite mecha¬ nical resistance and adequate reservoir volume for the electrolyte is met by the uniform walls made with suitable resistance and porosity .

At the embodiment according to Fig. 3 the tube walls are as mentioned somewhat thinner. Instead a separate electrolyte reservoir has been established by means of the separators 14 and 24, which complete the outer walls of the tubes at that side which faces the negative electrodes 12, 22. At the embodiment shown in Fig. 3 the total wall thickness around the tubes will be approximately uniform by means of the total thickness of the separators and the tube wall at the outerside and of the total thickness of the two connected tube walls at the inside .

At the embodiment according to Fig. 4 the wall thickness in the tubes is very insignificant and one can say that their main object is to meet with the demand that a sufficiently firm cover for the ac¬ tive substance while the electrolyte reservoir mainly is enclosed in porous separators , on the one hand the aforementioned between the positive and the negative electrodes and designed 14, 24 and on the other hand the pleated separator 38 which forms the inner reservoir 18.

Whichever embodiment is chosen can depend on factors such as requisite mechanical strength at specific cases of use, present re¬ sources of manufacture and access of material. The embodiment ac¬ cording to Fig. 4 is advantageous in that respect that the material used does not mean any compromise between mechanical strength and the ability to absorb liquid but can be made with specific characte¬ ristics in order to meet these two demands which can be difficult to meet in one and the same material.

By chosing a triangle form of the tubes it is established as afo¬ rementioned that the positive electrode wholly can form plane outer sides which can be placed on short distances , thus with the desirab¬ le thin electrolyte layer to the negative electrodes . At the same time a large inner electrolyte reservoir is obtained by means of the two inwards facing walls of each tube. This gives a construction which is advantageous with regard to the object of the invention. Naturally these advantageous characteristics can to a certain degree be obtained also with a form which somewhat deviates for the triangular one, such as an embodiment with the inner sides of the parts of the electrodes somewhat arched . Even such an embodiment is included in the scope of the invention.

A cell can also have a smaller acid supply 32 situated inside the negative electrode, by the fact that this has been made from two half plates with separators placed between the halves . At normal discharges the SO . ions manage to be transported to the negative electrode from the reservoir between the positive single electrodes . But at very high discharge current strength there might be a lack of SO. ions at the negative electrode and a reservoir can therefore be suitable. At extremely high discharges only so little of the active material in the acid in the separators is used and the pores of the negative electrodes are sufficient.

There is a number of more or less suitable materials for the separators and the reservoirs . The material must be micro porous in the separator and absorb with the largest possible effect in order to get an^* even density in the cell. It must be inert to oxygen in "statu nascendi" and the sulphuric acid and must not contain any damagable impurities . The most suitable material is glass fibre, avail¬ able in the market as 100% glass fibre with a fibre diameter less than 2μ in certain cases lμ . It looks like cotton and has a porosity over 95% even at hard compression. It is easily lyophiled by sulphoric acid and with good effect. In the reservoir, however, even certain permanent organic felt material can be used.

The reservoir of micro porous glass for the electrolyte has been described with a number of different forms . On the one hand the reservoir consists of a plane parallel plate between the two electrodes, on the other hand as a material in the triangle shaped tubes and finally as an interlayer between two parts of a tube plate between the tubes arranged in two lines in said plate. Moreover the micro porous material can be present also in other separators .

An essential factor when manufacturing these components per se as well as mounting of the electrodes to an accumulator, is the mechanical strength, especially the rigidity of the components . The micro porous material is in its initial condition of felted glass fibres a soft material with low mechanical stability. According to the invention, however, a better mechanical strength in a forming phase can be obtained . This is made by impregnating the micro porous glass_, felt with solutions of unorganic salts or oxides . After the impregnation the glass felt is dried and a hard and rigid plate or a block is ob¬ tained which can be worked mechanically . In order to increase the tensile strength the micro porous material can be mixed with longer and thicker non-micro fine glass fibres which will thereby act as an armament. Such fibres or braided nets of such fibres can also be placed to the below described compression of the surface layer of the blocks or plates . This can be considered especially suitable when the plates shall be profiled by folding or bending of the salt impreg¬ nated material.

Another essential characteristic beside the increased mechanical strength which is obtained by means of a salt impregnation is the armament in compressed condition which can be obtained if the im¬ pregnated micro porous felt is allowed to dry in compressed condition . After the material has been placed in the accumulator cell and the acid been filled the salt will namely be dissolved by the acid and the micro porous material will swell and fill all spaces so that no freely movable acid is present but all acid is present in a bound form. Fur¬ thermore the expanding felt will exercise a holding against pressure on those parts which during the charging of the accumulator and discharging will swell, for example the positive substance (PbO₂) .

It is suitable to use substances which, if they remain in the accumulator after dissolution in the acid, will not harm the function of the battery. In this case is is not necessary to remove the sub¬ stance from the glass fibre body before it is mounted in the accu¬ mulator. , It is advantageous from several points of view, on the one hand no particular leaching operation is necessary and on the other hand the increased mechanical strength is remained even during the continued handling after the forming and thereby during the moun¬ ting in the accumulator and finally is reached what has been mentio¬ ned above, that it is possible to make the micro porous material swell while absorbing electrolyte in formed pores in connection with the dissolution of the substance . The condition to let the substance dis¬ solve from the glass fibre body of the electrolyte after mounting is naturally what has been mentioned above , that the substance does not deteriorate the fuction of the electrolyte in the accumulator. Sulphates and silicates with cations comprising Na- , K- , Al- or MG-ions or mixtures of these can be used. As a number of these salts can be made to crystallize with water of crystallization they are to be preferred as these crystals seem to give an additional strength to the armament. Said sulphates have a good solubility in sulphuric acid of the concentration that is used in lead batteries and will therefore be completely dissolved. It is , however, possible for certain purposes to use such a great amount of salt impregnation and such a relatively small amount of sulphuric acid that a saturated solution arises, whereby only a small amount of the salt will be dissol¬ ved from the micro porous glass . A corresponding effect is obtained when using silicates with said cations which have a considerably more limited saturation in the sulphuric acid than the sulphate. Hereby it is also possible to obtain by means of local impregnations or repeated impregnations with different salts or salt mixtures different degrees of mechanical strength before as well as after the influence of the acid.

For instance the manufacture of impregnated micro porous glass block or plates can take place by means of fibres of C-glass , which are the most resistant to acid, and with a fibre diameter not larger than lOμ, being disperged in water. This water is sucked off through a net, in which the slurry of the glass fibres is collected. The felt obtained in this manner can have a thickness of 1 mm to 5 cm . The felt will now dry at a suitable temperature after which it is stretched between plane or profiled perforated plates. After that the pores in the micro porous material with the salt solution will be filled, which can be a 10-70% solution of any of the salts mentioned above.

After the impregnated material has been dried, it is loosened from its stretched condition and is now well suited for mechanical manipulation or further processing. If such a salt is used which crys¬ tallizes with water of crystallization , the drying should take place at a temperature which is lower than the one at which the salt melts in its water of crystallization.

It is also imaginable to add a more concentrated salt solution of for example silicate on the surfases of the micro porous blocks or plates, without for that reason impregnate the whole plate or block. By this procedure a stronger or smoother surface layer is obtained or a means for assembling different parts of the micro porous mate¬ rial .

At a suitable choice of profiled plates for stretching and drying V-shaped grooves can be formed as early as at this assembling.

In one manner to obtain triangle shaped tubes , as is shown in Figs . 2-4, longitudinal, V-shaped grooves are cut into a glass block 5-15 mm thick, by means of a sharp-edged blade to a pre-fixed depth and angle. The cut away material can be used again. If one intends , as is the case in connection with tube electrodes , to fill the electrode with a powder of some lead compound through openings in the sides of the glass block, plane impregnated plates are fixed over the sides of the glass block provided with the V-profiles after which a grid in the form of rods is inserted in the formed channels and the triangle shaped tubes are filled by vibration in a manner known per se . On the other hand, if it is desired to fill the V-shaped grooves with a lead compound of such a consistence which is used when manufactu¬ ring greased plates and which cannot be vibrated into the electrode, the grids are placed in the grooves on the one side and said compound is greased into the V-shaped grooves on this side, after which the side is sealed by means of an impregnated plate of micro porous glass . The method is repeated with the other side . It is natu¬ rally necessary to seal the open ends which takes place for instance by means of preshaped plugs of inert material. The mechanical working is not limited to slicing, but can also take place by cutting or sawing.

The manufacture of the profiles of micro porous glass , shown in Fig. 4, can also take place by folding or bending of the glass felt either so that the profiles are formed before the impregnation whereby compression takes place in mandrels made for this purpose, or so that the impregnated plates are softened before shaping and then drying again . Such a softening can take place locally, for in¬ stance along a folding line by adding water in a narrow zone . By this procedure the drying time can be shortened.

In this way it is also possible to shape tubes of the shape as shown in particularly Fig. 2 in continuous lengths by a strip of an impregnated plates folded along two lines and its free edge portions are joined by means of silicate or in any other way known per se . Example 1

50 grammes of glass fibres <6μm thick is disperged in 2,5 litres of water by vigorous stirring. The suspension is poured into a tube shaped container 50 cm high and with a diameter of 16,5 cm and in the bottompart of which is a wire cloth No . 100 mesh. The container contains 2,5 litres of water. By opening a valve in the bottom of the container the suspension of glass fibres can be brought to be collected in the net in a partly compressed form. The felt cake is removed from the wire and is removed from water by compression and brought to a heating chamber for drying at 80°C during 24 hours . After that the fibre substance is placed between two plane double walled and perforated plastic plates with a thin cloth of poly- prop ylen as interlayer. The plastic plates are pressed together with pairwise attached U-profiles of aluminum to a thickness of 10,5 mm. A solution of 100 g/1 sodium sulphate with water of crystallization and lOOg/1 aluminum sulphate with water of crystallization is added to the glass block till all the pores are filled with the solution . Dry¬ ing takes place during 48 hours at 80°C, after which a rigid and hard block is obtained from which V-shaped grooves can be cut to a depth of 6 mm and an angle of 45 degrees on both sides of the block. The method has been described at a laboratory level but can easily be adjusted for mass production by the man skilled in the art.

Claims

Paten tkrav:

1. Electric accumulator, particularly lead accumulator comprising a cell with a container (2, 4) impervious to electrolyte and gas, at least one positive porous electrode ( 16) , at least two porous nega¬ tive electrodes (12, 22) and electrolyte at an amount enough for the discharge degree which is desired, whereby the positive electrode (16) comprises at least two parts (25, 26) each one formed as tube plates with a common upper frame (19, 20) , CHARACTERIZED BY the parts of the positive electrode (16) each one consists of mainly triangle shaped tubes (25, 26) with a flat side at some of the tubes close to the one negative electrode and a flat side at the remaining tubes close to the other negative electrode (12, 26) and that in the area(s) where the remaining triangle sides of the parts of the posi¬ tive electrodes meet there is a micro porous material comprising an acid reservoir (18) , which is arranged to receive a predetermined amount of electrolyte, which together with the electrolyte in the po¬ rous electrodes and in the present remaining areas for receiving elec¬ trolyte constitutes an amount sufficient for the discharge degree which is intended .

2. Electric accumulator according to claim 1 , CHARACTERIZED BY the cell beyond micro porous material in said areas also have separators (14, 24) of said micro porous material between the negative electrodes (12, 22) and the said flat sides of the positive electrode (16) .

3. Electric accumulator according to claim 1 or 2, CHARACTERIZED BY a separator thickness between 0, 1-3 mm .

4. Electric accumulator according to claim 3, CHARACTERIZED BY a separator thickness between 0,5-2 mm .

5. Electric accumulator according to claim 1, 2, 3 or 4, CHARACTE¬ RIZED BY the total inner porous volume in electrodes (12, 22, 16) , tube walls and the present separators is larger than the volyme of the electrolyte.

6. Electric accumulator according to any of the preceding claims, CHARACTERIZED BY the tubes in the positive electrode (16) are made from micro porous material which at least partly constitutes the acid reservoir (18) .

7. Electric accumulator according to any of the claims 1-4, CHA¬ RACTERIZED BY the tubes in the positive electrode (16) are made from felted, braided or woven material and that a thicker micro porous material (14, 24/38) is fixed on the outside of the tubes thereby constituting said acid reservoir.

8. Electric accumulator according to claim 7, CHARACTERIZED BY the tubes in the positive electrode (16) has a thin thickness of mate¬ rial and are arranged in two rows where one triangle side forms said flat outer sides , whereby between the inner sides formed by the two remaining sides of the tubes are arranged a porous separator (38) which is formed according to said inner sides .

9. Electric accumulator according to any of the preceding claims , CHARACTERIZED BY the volyme of the electrolyte is 80-98% of the total pore volyme in the electrodes (12, 22 16), in the present said separators (14, 24) oc in the absorbing material (38) between the parts of the positive electrodes (16) .

10. Electric accumulator according to claim 9, CHARACTERIZED BY the volyme of the electrolyte is 90-95% of the total pore volume.

11. Method for manufacture of micro porous parts (12, 22, 16, 14, 24, 38) for an electric accumulator according to any of the claims 1-10 och comprising a cell with an electrolyte and gastight container (2, 4), at least one positive porous electrode (16) , at least two porous negative electrodes (12, 22) and electrolyte to an amount sufficient for the discharge degree that is desired, said positive electrode (16) comprising at least two parts (25, 26> each shaped as tube plates with a common upper frame (19, 20) with the parts of the positive electrode (16) each formed by mainly triangle shaped tubes (25, 26) with a flat side at some of the tubes close to the negative electrode and a flat side at the remaining of the tubes close to the other nega¬ tive electrode (12, 26) , and that in the area(s) where the remaining triangle sides of the parts of the positive electrodes meet there is a micro porous material constituting an acid reservoir (18) , which is arranged to receive a predetermined amount of electrolyte, CHARAC¬ TERIZED BY a fibre body (12-38) mainly of glass fibre being provi¬ ded with an impregnation of a substance such as a metal salt in or¬ der to provide it with mechanical stability at its forming.

12. Method according to claim 11, CHARACTERIZED BY the substance is adjusted to be received by the electrolyte of the accumulator and to be integrated in the same without any damage to the function.